refactor: Enhance GenerationJobManager with improved subscriber handling

- Updated RuntimeJobState to include allSubscribersLeftHandlers for managing client disconnections without affecting subscriber count.
- Refined createJob and subscribe methods to ensure generation starts only when the first real client connects.
- Added detailed documentation for methods and properties to clarify the synchronization of job generation with client readiness.
- Improved logging for subscriber checks and event handling to facilitate debugging and monitoring.

packages/api/src/stream/implementations/InMemoryEventTransport.ts

@@ -43,6 +43,10 @@ export class InMemoryEventTransport implements IEventTransport {
     state.emitter.on('done', doneHandler);
     state.emitter.on('error', errorHandler);
 
+    logger.debug(
+      `[InMemoryEventTransport] subscribe ${streamId}: listeners=${state.emitter.listenerCount('chunk')}`,
+    );
+
     return {
       unsubscribe: () => {
         const currentState = this.streams.get(streamId);
@@ -90,7 +94,9 @@ export class InMemoryEventTransport implements IEventTransport {
    */
   isFirstSubscriber(streamId: string): boolean {
     const state = this.streams.get(streamId);
-    return state?.emitter.listenerCount('chunk') === 1;
+    const count = state?.emitter.listenerCount('chunk') ?? 0;
+    logger.debug(`[InMemoryEventTransport] isFirstSubscriber ${streamId}: count=${count}`);
+    return count === 1;
   }
 
   /**